A common light source of optical interconnect modules is the vertical-cavity surface-emitting laser (VCSEL). A VCSEL is a type of semiconductor laser with a beam emission perpendicular to the surface of a semiconductor chip. The reliability of commercially available VCSEL devices has improved substantially during the last decade. Nevertheless, during various burn-in processes or highly accelerated stress tests, the most common mechanism for VCSEL degradation remains the dark line defect (DLD) from dislocations. A variety of techniques was made available to detect degraded (dark) VCSEL devices. Most of these techniques are destructive in nature (cause irreversible changes), which makes them unsuitable as a screening method, and/or make use of elaborate and expensive instrumentation. One testing method is by use of Transmission Electron Microscopy (TEM). Unfortunately, atomic resolution images come at a great cost and the technique is destructive. Another testing method is Thermally Induced Voltage Alteration (TIVA) which could be a non-invasive technique with a relatively good resolution when used with laser scanning microscopy (LSM). Unfortunately, both TEM and LSM remain analysis techniques that are expensive and mostly unavailable to the ubiquitous characterization laboratory.
In view of the foregoing, there is a need for a more efficient and intelligent method of diagnosing and screening optical interconnect light sources that gives high resolution and that is highly cost effective.